1. Field of the Invention
The present invention relates to an elevator, and more particularly to a double screw elevator.
2. Description of the Prior Art
Nowadays, elevators have become indispensible to our daily life, and most of the conventional elevators are driven by steel rope. However, the steel rope elevators require frequent and regular maintenance, otherwise, the steel rope may break, causing injury or death.
Another screw type elevator 10, for example the one disclosed in TW Pt 543649, as shown in FIG. 1, comprises a fixed screw assembly 11, a relay screw assembly 12 and an elevator-car screw assembly 13 which are connected in series and are electrically connected with and driven by a power source 111, 121, 131, respectively. The elevator-car screw assembly 13 is driven by the power source to make the elevator car 14 move linearly. The screw driving method reduces the occurrence of accident, and the serially-connected screw assemblies reduce the required length of a single screw, and thus making it easier to manufacturing the screw. However, the screw assemblies each require a power source and are then connected in series, which complicates the structure and assembly of the elevator.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.